What is the best way to make a scene look like the inner of the colon?
To answer your question about the camera, you could do either. Try inputting the specifications of the camera you are using, and see if it looks right, otherwise I would recommend Panoramic set to Fisheye Equisolid. You can play with the aperture and FOV settings from there.
For the material/ reflections, you can try this:

Basically What I did was warp the vectors of a couple of Voronai Textures with a noise texture that I softened by mixing it heavily with light grey.  I offset one of them, and colored them red and blue respectively, to make the veins. I also attempted to cancel some of the vein continuity by mixing in another Noise Texture, but looking at it now, I think I needed to darken the noise with a ColorRamp first.

I made the wall color by connecting a ColorRamp to another noise texture, and used a Musgrave Texture to make the inner wall bumps. I softened the Musgrave and plugged it into the height input of a bump node to get some normal information. Before this, I mixed in some height information from the veins as well. I also inverted this mix and darkened the contrast to use as a roughness input - this, combined with the normal map is a large basis for the reflections.  Lastly I mixed the colors together to use as both the BaseColor and the Subsurface color.

I set my Principled  BDSF as shown below. I made this in EEVEE, but it works just as well in Cycles - just note that you may have to turn down the transmission, subsurface, and maybe even metallic to make it look correct.

The end result looks like this:

I'll upload the blend file if you want to see for yourself - Keep in mind this is for 2.83, so it will likely not work in 2.79 unfortunately due to my use of Vector Math nodes, which I think 2.79 may lack (correct me if i'm wrong). If you can obtain and use 2.83, I would heavily recommend it.
File is here - 
Cheers